1. Field of the Invention
The present invention relates to multilayer substrate modules mounted in communication devices such as cellular phones.
2. Description of the Related Art
In the related art, various known multilayer substrate modules are known are mounted in communication devices such as cellular phones. A multilayer substrate module of the related art includes a multilayer circuit substrate formed of a plurality of layers stacked on top of one another with conductor patterns being formed on the layers; a mounting land formed on one main surface of the multilayer circuit substrate; and an input/output terminal formed on the other main surface of the multilayer circuit substrate. A wiring line that connects the mounting land and the input/output terminal to each other, and a ground conductor are formed of conductor patterns inside the multilayer circuit substrate.
In recent years, the distance between the wiring line, which is connected to the input/output terminal, and the ground conductor has tended to become smaller in such multilayer substrate modules as the profile of the multilayer circuit substrate has decreased. Consequently, there has been a problem in that a capacitance is generated between the wiring line and the ground conductor, the impedance of the input/output terminal becomes capacitive and insertion loss (IL) is increased due to impedance mismatching.
Consequently, in Japanese Unexamined Patent Application Publication No. 2011-77723, a multilayer substrate module is disclosed in which an inductor that is connected to an input/output terminal is formed inside a multilayer circuit substrate in order to improve matching.
However, when an inductor is formed inside a multilayer substrate module and the inductor is close to a ground conductor as in Japanese Unexamined Patent Application Publication No. 2011-77723, a magnetic field is generated by the inductor when a signal is transmitted through the inductor and an eddy current is generated in the portion of the ground conductor that faces the inductor. In particular, in a multilayer substrate module having a low profile structure, the distance between the inductor and the ground conductor is even smaller and therefore the eddy current is larger.
Consequently, in the multilayer substrate module of Japanese Unexamined Patent Application Publication No. 2011-77723, there is a problem in that the Q value of the inductor is degraded and an IL improvement effect is not sufficiently obtained.